Polymer electrolyte fuel cells that utilize hydrogen are well known and have been proposed for use as energy sources in automobiles. As these cells can only consume hydrogen, to utilize liquid fuels, reforming of the fuel to hydrogen and carbon monoxide/dioxide and oxidation or scrubbing of the carbon monoxide, which poisons the system at very low levels, is required.
Solid oxide fuel cells are well known, but have been limited to power sources that are not temperature cycled repeatedly. To be useful for an automotive power plant, a fuel cell needs to become operational quite fast, preferably faster than 5 minutes, more preferably less than two minutes and even more preferably less than 30 seconds. Energy requirements to keep a high temperature solid oxide type fuel cell hot all the time in an auto are prohibitive. Hence, as fuel cell would need to be heated almost every time an auto was used, the cell would need to withstand perhaps as many as 10 to 20 thousand heating cycles. Until now no inorganic electrolyte solid oxide fuel cell has been designed having sufficient thermal shock and thermal cycling resistance to be considered for this application.
Flexible thin ceramics have been described for example in co-assigned U.S. Pat. No. 5,089,455, some compositions of which would be useful electrolytes for fuel cells. Recently, U.S. Pat. No. 5,273,837 has described the use of such compositions to form a thermal shock resistant fuel cell. Nowhere in these documents is the application of these compositions and these fuel cells for automotive power plants mentioned. Thin corrugated ceramic structures have been disclosed as fluid heaters in U.S. Pat. No. 5,519,191.
The foregoing discussion is intended to show use of zirconia as an electrolyte is known, and use of ((LaSr)MnO.sub.3) and other expansion matched electrically conducting perovskite structures are known for use as air side electrodes, as well as use of zirconia/nickel composites for fuel side electrodes. In addition, metals, intermetallics and LaCrO.sub.3 have been used for interconnect structures. Notwithstanding, there continues to be a need for improved solid oxide fuel cells, particularly fuel cells capable of withstanding very high heating and/or thermal cycles. This is the focus of the present invention.